Miniaturization is a main objective of many of today's electronic component developers and manufacturers, especially those who design and develop semiconductor chips. Today's chips contain many times the number of connections of chips of just a few years ago, and further miniaturization efforts are ongoing. Accordingly, developers of various electronic packages (e.g., chip carriers) and printed circuit boards (or cards) have been similarly pressed to provide higher density connections to accommodate the chip or chips designed for being mounted thereon and electrically coupled thereto.
Typically, such chips and corresponding electronic packages utilize extremely small conductive members such as spherically-shaped solder balls as the connecting medium. Such solder balls may possess a diameter of only about 0.003 inch to about 0.006 inch, and in the final product for incorporation within a larger electronic structure (e.g., a microprocessor), are typically arranged in compact, highly dense arrays (e.g., those with the balls positioned apart on only 0.006 inch centers). The electrical circuitry for such packages is also highly dense, and may possess line widths as small as about 0.002 inch, with 0.002 inch spacing between lines. Even smaller elements are presently being contemplated for future products.
It is readily understood that testing of such devices, packages, and the like is a critical and necessary step during the manufacture thereof, in order to prevent subsequent failure when the chip and its corresponding package and associated printed circuit board are utilized in a larger (and often very expensive) assembly such as a microprocessor (e.g., computer server or mainframe). It can also be appreciated that such testing can be a difficult, complex and time-consuming operation.
Examples of various printed circuit board (substrate) structures as well as means for testing electronic structures are illustrated in the following U.S. Letters Patents.
In U.S. Pat. No. 6,828,510, entitled “Multilayered Printed Wiring Board And Method Of Manufacturing Multilayered Printed Wiring Board”, issued Dec. 7, 2004, there is described a multilayered board structure in which a “core” substrate is formed having a metal layer sandwiched between two dielectric layers. Plated through holes (PTHs) are formed in the dielectric layers using lasers and the interim conductor, being metal, apparently helps to determine the hole depth. A specific bismaleimide-triazine (BT) resin (called “refractory” in one embodiment in the patent) is used, which, according to this patent, includes soluble particles dispersed therein. An “interlayer” resin insulating layer is built up on the “core” substrate. Immersion in electro-less plating solution is described as a means for plating the PTH side walls.
In U.S. Pat. No. 6,816,385, entitled “Compliant Laminate Connector”, issued Nov. 9, 2004, there is described a flexible shear-compliant laminate connector having a plurality of contacts formed on a first surface and second surface of the connector, wherein select contacts on the first surface of the connector are off-set from select contacts on the second surface of the connector. The laminate includes a core comprising copper-invar-copper (CIC), or other similarly used material, such as copper, stainless steel, nickel, iron, molybdenum, etc. The core has a thickness in the range of approximately 1-3 mils. The choice of core material depends upon the material within the chip package being attached thereto. For a ceramic chip package, having a relatively low CTE, the overall CTE of the laminate may be about midway between the card and the chip package. According to this patent, this provides improved distribution of stress, and therefore a reduction of stresses within the BGA connections and the interconnection.
In U.S. Pat. No. 6,529,022, entitled “Wafer testing interposer for a conventional package”, issued Mar. 4, 2003, there is described a wafer testing interposer. The interposer comprises a support having an upper and a lower surface. One or more solder bumps are on the lower surface. One or more first electrical terminals are on the upper surface, substantially corresponding to the position of the solder bumps, and forming a pattern. One or more first electrical pathways pass through the surface of the support and connect the solder bumps to the first electrical terminals. One or more second electrical terminals are on the upper surface of the support. The second electrical terminals are larger in size and pitch that the first electrical terminals, and these are located within the pattern formed by the first electrical terminals. One or more second electrical pathways connect the first electrical pathways to the second electrical pathways.
In U.S. Pat. No. 6,383,005, entitled “Integrated circuit socket with contact pad”, issued May 7, 2002, there is described an integrated circuit socket having a contact pad. The integrated circuit socket includes a base unit, consisting of a base, contact pins and an elastomer. The contact pins provide electrical contact of the other elements and the elastomer provides the compactness of the assembly. The socket further includes an interposer, consisting of a flexible film, a stiffener and a stop layer wherein the contact pad of the flexible film may contact with the solder ball of the IC device to buffer the pressure formed by a tight contact when the IC device is moving downward. The socket also consists of an adapter unit and a cover.
In U.S. Pat. No. 6,333,563, entitled “Electrical interconnection package and method thereof”, issued Dec. 25, 2001, there is described an electrical interconnection package and a method for using same which allegedly increases the fatigue life of a Ball Grid Array (BGA) electrical interconnection. (Such BGAs include, understandably, solder balls of the type mentioned above, and interconnect components of the type also mentioned above.). This described structure includes an organic interposer using a high modulus under-fill material to couple an electronic “module.” The organic interposer is then joined to an organic board (PCB) using standard joining processes. The “module” can be removed from the organic board at any time by removing the organic interposer using standard rework techniques.
In U.S. Pat. No. 6,309,915, entitled “Semiconductor chip package with expander ring and method of making same”, issued Oct. 30, 2001, there is described a method of making a semiconductor chip assembly, including providing a dielectric element with a plurality of electrically conductive terminals, disposing an expander ring over the dielectric element so that a semiconductor chip on the dielectric layer is disposed in a central opening in the expander ring, and disposing an encapsulant in the gap between the expander ring and the semiconductor chip. The size of the gap is controlled to minimize the pressure exerted on the leads by the elastomer as it expands and contracts in response to changes in temperature. The semiconductor chip and expander ring may also be connected to a heat sink or thermal spreader with a compliant adhesive.
In U.S. Pat. No. 6,156,484, entitled “Gray Scale Etching For Thin Flexible Interposer, issued Dec. 5, 2000, there is described a sculpted probe pad and a gray scale etching process for making arrays of such probe pads on a thin flexible interposer for testing the electrical integrity of microelectronic devices at terminal metallurgy. Also used in the etching process is a fixture for holding the substrate and a mask for single step photolithographic exposure. The result is an array of test probes of pre-selected uniform topography, which make contact at all points to be tested simultaneously and nondestructively. The pad is retained within a dielectric body and includes a “domed” portion and an opposing “sculpted” portion which is formed using etching, resulting in “features” having “sculpted” areas. Both portions are part of an integral structure, such that these are of a single metallic body and arranged in an opposing orientation with one portion being directly opposite the other.
In U.S. Pat. No. 6,051,982, entitled “Electronic component test apparatus with rotational probe and conductive spaced apart means”, issued Apr. 20, 2000, there is described a test apparatus including at least one probe member precisely aligned using two spaced apart means (e.g., thin layers) such that the probe can effectively engage a conductor (e.g., solder ball) on an electronic module (e.g., ball grid array package). A compressible member (e.g., elastomeric body) is used to bias the probe toward the conductor. Various probe cross-sectional configurations are also provided. As taught herein, the probe electrically contacts one of the spaced apart means, also conductive, to thus form a circuit which can extend externally of the apparatus (e.g., for connecting to appropriate testing equipment).
In U.S. Pat. No. 5,880,590, entitled “Apparatus and method for burn-in and testing of devices with solder bumps or preforms”, issued Mar. 9, 1999, there is described an apparatus for providing temporary connections to a flip-chip style chip having solder bumps or pre-forms protruding there-from for testing and burn-in while avoiding distortion of the bumps or pre-forms and avoiding wear and damage to a test or burn-in jig such as a ball grid array. The apparatus uses a resilient bucketed interposer which includes recesses which have a depth greater than the protrusion of the solder bumps or pre-forms and, preferably are narrowed at one side to a tear-drop shape. Metallization in the recesses and contacts on the interposer which mate with the jig are preferably textured with dendrites to be self-cleaning. A beveled tongue and groove arrangement translates a slight compressive force to a slight shearing force between the interposer and the chip to ensure good connections to the protruding solder bumps on the chip. Any deformation of the bumps thus tends to only improve accuracy of positioning of the bumps and avoids solder voiding due to compression distortion. Full burn-in and functional testing can then identify “known good” chips or dies before package completion, particularly to avoid rework of modular circuit packages.
In U.S. Pat. No. 5,641,945, entitled “Contacting structure with respect to spherical bump”, issued Jun. 24, 1997, there is described a contacting structure with respect to a spherical bump in which the spherical bump is to be contacted with a contact pin, the contact pin including a contacting portion supported by a resilient support element. The contacting portion is arranged in opposite relation to that part of a spherical surface of the spherical bump other than a lower-most point thereof. The contacting portion has a projection capable of pressing into the spherical surface of the spherical bump, and also has a pressure receiving surface for setting an amount by which the projection presses into the spherical surface.
In U.S. Pat. No. 5,528,159, entitled “Method and apparatus for testing integrated circuit chips”, issued Jun. 18, 1996, there is described a method and apparatus for testing semi-conductor chips which include Input/Output (I/O) contacts. The apparatus is provided with an interposer that has contacts corresponding to the contacts on the semiconductor chip. Both the chip and the interposer contacts can be any known type including metal ball, bumps, or tabs or may be provided with dendritic surfaces. The chip contacts are first brought into relatively loose temporary contact with the contacts on the interposer and then a compressive force greater that 5 grams per chip contact is applied to the chip to force the chip contacts into good electrical contact with the interposer contacts. Testing of the chip is then performed. The tests may include heating of the chip as well as the application of signals to the chip contacts. After testing, the chip is removed from the substrate.
In U.S. Pat. No. 5,391,995, entitled “Twisting electrical test probe with controlled pointing accuracy (Johnston), issued Feb. 21, 1995, there is described a spring biased test probe for testing electrical printed circuit boards which includes an elongated tubular barrel having an open end, and a compression spring within a spring seating end of the barrel, opposite from its open end. A plunger inserted in the barrel reciprocates during testing, sliding within the barrel and biased by the spring pressure. The plunger includes a forward end portion outside the barrel, a slidable tail portion that contacts the spring and slides within a barrel, and an intermediate twisted portion between the forward end and the tail portion of the plunger. The forward end of the plunger has a probe tip configured to make frictional pressure contact with the board to be tested. The intermediate portion is twisted about its axis to form a spiral with helical grooves contacted by circumferentially spaced apart crimps in the side of the barrel, adjacent the open end of the barrel. The plunger is rotated about its axis by its contact with the crimps as the plunger travels axially in the barrel. The twisted intermediate section of the plunger and the forward end of the plunger extend outside the barrel which is contained in an elongated tubular outer receptacle. The forward end of the plunger includes an elongated enlarged diameter guide bearing section between the probe tip and the twisted section of the plunger.
In U.S. Pat. No. 5,207,585, entitled “Thin Interface Pellicle For Dense Arrays Of Electrical Interconnects”, issued May 4, 1993, there is described a thin interface pellicle probe for making temporary or permanent interconnections to pads or bumps on a semiconductor device wherein the pads or bumps may be arranged in high density patterns. The electrode for each pad or bump has a raised portion for penetrating the surface of the pad or bump to create sidewalls to provide a clean contact surface. The electrode also has a recessed surface to limit the penetration of the raised portion. The electrodes may be affixed to a thin flexible membrane to permit each contact to have independent movement over a limited distance and of a limited rotation. In one embodiment (FIG. 22), the electrode's opposing ends are offset from one another to permit the electrode to “rotate” slightly when force is applied, resulting in a desired wiping engagement.
In U.S. Pat. No. 4,105,970, entitled “Test Pin”, issued Aug. 8, 1978, there is described an electrical testing pin characterized by a crown with an inner contact area and a plurality of outer contact areas, the former extending longitudinally beyond the latter. The pin includes a crown with a multiplicity of spaced sharp contacts including a central sharp contact and a multiplicity of sharp contacts spaced there-around in a contact set, each contact of the set being separated from adjacent contacts by continuous radial grooves extending uninterruptedly at an angle to define two of the sharp contacts of the set and also to allow for self-cleaning.
When simultaneously testing pluralities of conductive members such as the above-described extremely small solder balls arranged in a highly dense array, it is quickly understood that precise alignment of each test probe member is critical, especially during periods of force application. To establish electrical connection between the conductive members and the solder balls, it is necessary to provide sufficient force to penetrate the non-conductive metal (e.g., tin) oxide coating on the surface of the solder balls. It is further understood that excessive application of such forces can damage or even destroy the relatively delicate solder balls such that it is not possible to re-establish their spherical shape, even with attempts to reflow the balls at temperatures above the melting point of the solder. In addition, excessive application of such forces can either exceed the capability of the tester, cause deformation of the wafer, or cause damage to the integrated circuit device. Clearly, these probes must maintain a spaced relationship from one another (or shorting can occur during test), and must also allow ease of movement of the individual probes toward and away from the object being tested. It is critically important that these probes do so during periods of force application in which the forces may become somewhat excessive, to the point that if compensation does not occur, solder ball damage or even destruction may result. It is not believed that the test apparatus described in the above patents (or the substrates also described in some) are able to provide such connection and movement in an effective and cost-efficient manner capable of meeting many of today's demanding production schedules.
It is believed, therefore, that a method of making a test apparatus interposer capable of effectively interconnecting highly dense arrays of conductive members such as small diameter solder balls in a precise, yet expedient manner such as taught herein, would constitute a significant advancement in the art.